Urban development without more mobility by car lessons from amsterdam, a multimodal urban region

Environment and Planning A 2003, volume 35, pages 575 ^ 589

DOI:10.1068/a3592

Urban development without more mobility by car?

Lessons from Amsterdam, a multimodal urban region Luca Bertolini, Frank le Clercq

AMEĂśAmsterdam Study Centre for the Metropolitan Environment, Universiteit van Amsterdam, Nieuwe Prinsengracht 130, 1018 VZ Amsterdam, The Netherlands; e-mail: l.bertolini@frw.uva.nl, fcl@tg.nl Received 30 March 2002; in revised form 3 October 2002

Abstract. The fundamental dilemma in attempts to make urban development less dependent upon mobility by car is the inability of alternatives to match the quality of accessibility provided by private motorized transport. Failure to recognize this means that bringing about environmentally more sustainable urban mobility patterns is only possible at economic, social, and political costs that are unacceptable in most societies. In this paper we identify and discuss ways out of this dilemma, in the form of solutions that pursue the goal of increasing both sustainability and accessibility. We start by contending that what people ask is not a generic mobility, but rather opportunities to participate in spatially disjointed activities. Accordingly, accessibility should be defined as the amount and the diversity of `spatial opportunities' that can be reached within a certain amount of time. Solutions to the accessibility ^ sustainability dilemma building upon this perspective (that is, planning concepts, policy measures) have been the object of recent research at the Universiteit van Amsterdam and are discussed and we look for, and find, evidence of the feasibility of these solutions in the actual trends in the Amsterdam urban region. Some policy implications of the findings are discussed.

1 Introduction Transport is a central aspect of the sustainable urban development debate. Urban transport has major impacts on the local (and the global) environment, as well as on the quality of life in, and the economic performance of, cities. Because so many things come together when dealing with urban transport, the subject is highly complex. Direct measures such as energy use, CO2 emissions, air pollution, traffic noise, and the like would be the best indicators of the environmental impact of urban transport. However, these measures are rarely available; hence, the `per capita distance traveled by car' is the most widely accepted (un)sustainability indicator of urban transport (Wegener and FuÂŤrst, 1999). This indicator is highly correlated with the aforementioned negative environmental impacts, and also with other sustainability aspects (see, for instance, Newman and Kenworthy, 1999). In a wider perspective, in which economic and social issues are also considered, Newman and Kenworthy (1991) define the unsustainability of current urban transport patterns as `automobile dependence'. From this perspective, the challenge for sustainable urban transport and land-use planning becomes that of achieving urban development with no, or at any rate with as little as possible, increase in car use.

There is, however, a fundamental dilemma when trying to make urban development less dependent on the car: the inability of most alternatives to match the quality of accessibility provided by private motorized transport. Failing to recognize this means that bringing about more sustainable urban mobility patterns is only possible at economic, social, and political costs that are unacceptable in most societies. Our goal in this paper is the identification and discussion of ways out of this dilemma, in the form of solutions that pursue the goal of increasing both sustainability and accessibility. Our starting point is the observation that what people ask is not so much a generic mobility but, rather, opportunities to participate in spatially disjointed activities. Solutions to the

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accessibility ^ sustainability dilemma building upon this perspective are the object of current research at the Universiteit van Amsterdam and are discussed in the first part of the paper. We build upon these findings to sketch an environmentally more sustainableĂśbut economically no less competitive, and socially and politically no less acceptable Ăśvision for the integration of sustainable transport and land-use patterns in urban development strategies. In the second part of the paper we look for, and find, evidence of the feasibility of these solutions in the current mobility and activity trends in the Amsterdam urban region. We then introduce some policy implications of these findings.

2 The goal: from catering for mobility to providing spatial opportunities The pursuit of sustainability cannot be considered separate from an economic, social, and political context where other goals are equally, if not more, important. In all realworld situations, sustainability will never be the only goal, and may often not even be the dominant goal but will, rather, be weighed against other policy goals such as economic competitiveness or social equity. This means that multidimensional solutions, that is, solutions that succeed in serving several goals at the same time, will invariably be the ones with the greatest chance of success. The implication for our objective in this paper is that the most promising solutions will be those that succeed in combining sustainability with other goals. Most important in this respect is the goal of improving accessibility, that is, the basic reason for a transport system to exist. Even though there are also other conceivable goals for the development of an urban transport system (in the Netherlands, for instance, `livability' and `safety' are often considered), the combination of the goals of sustainability and accessibility is central to overcoming the friction among major environmental issues, social aspirations, and economic imperatives mentioned in the introduction.

Having defined the objective as that of developing transport strategies and land-use strategies that maximize the synergy between sustainability and accessibility, the next step is to define both in a sound yet workable way. In our definition, sustainability entails that as little nonrenewable resources as possible are consumed, and that as few harmful emissions as possible are released. In the current and foreseeable context, this means an urban transport system characterized by: (a) as few car-kilometers as possible, (b) as efficient and clean car-kilometers as possible.

In more general terms: (a) as little motorized traffic as possible (this includes transit), (b) as efficient and clean motorized traffic as possible.

Translated into policy objectives this amounts to (in order of priority): (1) increasing as much as possible the opportunities for walking and cycling; (2) when walking and cycling are not realistic possibilities, increasing as much as possible the opportunities for transit while at the same time improving the environmental performance of transit (for example, cleaner and more efficient engines, shorter journey distances); (3) when transit is also not a feasible option, improving the environmental performance of the car.

In order to define accessibility adequately the introduction of three assumptions about human behavior is required, all of which are well supported by research (see, in particular, Downes and Emmerson, 1985; HaÂŤgerstrand, 1970; Schafer and Victor, 1997; Zahavi, 1974):

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(a) For the most part people travel not just for the sake of it, but in order to participate in spatially disjointed activities (for example, living, working, shopping, visiting in different places). (b) People want to have a choice among as large a number and as diverse a range of activities as possible. (c) Travel costs, and particularly travel time rather than travel distance, set a limit to these possibilities (in the form of total daily travel-time budgets, travel-to-work time budgets, etc).

According to these assumptions, accessibility can be defined as `the number and the diversity of places of activity that can be reached within a given time limit'. The goal of maximizing the synergy between sustainability and accessibility can be expressed as the goal of: Developing conditions for as large as possible a share of the more environmentally friendly modes in urban mobility, while at the same time maintaining, and possibly increasing, the amount and the diversity of activity places that can be reached within an acceptable travel time.

3 Concepts for sustainable transport and land use The goal formulated above is a useful reference when identifying promising sustainable transport and land-use concepts. In general terms, the sustainability-with-accessibility goal can be achieved if households and firms can link the same or a greater number and diversity of places of activity other than by car: (a) without travel, (b) by walking or cycling, (c) by transit, (d) or by the more efficient use of (cleaner) cars.

A shift of urban mobility and activity patterns in this direction has implications both for transport and for land-use policy, as schematically illustrated in figure 1.

Examples of transport-policy implications are facilitating walking and cycling by developing dedicated infrastructure (footpaths, bicycle paths), improving the speed Transport implications

Activity coupling

Land-use implications

without travel

Develop multifunctional homes and workplaces

walking/cycling

Develop multifunctional neighborhoods

Selectively increase average door-to-door speeds, and/or flexibilize transport supply

by transit

Further more selective use, and `cleaner' technologies, for example, through price or physical design

Promote transitoriented development, for example, functional concentrations at nodes

by car

Facilitate, for example, through physical design

Figure 1. Policy implications of sustainable urban mobility patterns.

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and especially the flexibility of transit (as with light rail systems), stimulating the introduction of cleaner engine technologies and the more efficient use of the car (for example, through car-pooling or car-sharing programs). An accompanying, highly effective, transport-policy measure is, of course, in all cases the (selective) discouragement of car use: for instance, through parking regulations, road pricing, or physical design. Examples of land-use policy implications include the development of multifunctional homes and workplaces, for example, facilitating teleworking; the development of multifunctional neighborhoods allowing walking or cycling to workplaces, shops, or other facilities; and orientating the spatial development of urban regions to public transport networks, as in `transit-oriented development' (Calthorpe, 1993; Cervero, 1998).

A variety of transport and land-use packages can be derived from these policy implications. Local conditions will largely determine which are the most effective.

However, some guiding principles can be identified and are introduced below.(1) It is important to underline that these should by no means be seen as blueprints, but rather as visualizations of potential directions. Furthermore, the focus on the supply side of transport and land-use measures should not obscure the fact that demand-management measures, such as pricing of car use, are also an essential part of successful strategies (see, among others, Bertolini et al, 2000; Wegener and FuÂŤ rst, 1999).

The central idea informing the following is that the quality of the accessibility of a given location has to be matched by the sort of activity to be located there, exploiting all sorts of transport modes. We define this philosophy as `multimodal urban ^ regional development'. In this perspective, two dimensions are especially important: the spatial reach of an activity or function (or its market or `catchment' area, expressed, for example, in kilometers) and its intensity of use (which may be expressed as inhabitants, workers, and/or visitors per unit of space and/or time). Given these two dimensions,

Activity feature: spatial reach Transport feature: speed Car environments

Transit environments

Walking and cycling environments

Activity feature: intensity of use Transport features: capacity (increasing), flexibility (decreasing)

Figure 2. Principles of multimodal urban ^ regional development: conceptual scheme.

(1)

Analogous principles have been and are being introduced, discussed, and elaborated in an evolving body of literature. See, for instance, Bertolini, 1999; Bertolini and Dijst, 2003; Breheny and Rookwood, 1993; Calthorpe, 1993; Cervero, 1998; Goudappel Coffeng, 1999a; Hall and Ward, 1998; le Clercq and de Vries, 2000; Meijers, 2000; Ministerie van V&W, 1995; Newman and Kenworthy, 1999; VHP and Goudappel Coffeng, 1999.

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the features (for example, speed, flexibility, capacity) of the available transport modes determine the preferred location of an activity, as illustrated in figure 2. At and around transit nodes belong activities with a spatial reach matching the scale of operation (and thus the speed) of the transit system and a high intensity of use (for example, concentrations of office, leisure, shopping). Acceptable travel times to and from the transit node determine the extent of the `nodal areas' where origins (homes) and destinations (work, free-time), respectively, are located. Cycling and walking are the most suitable travel modes for activities with a low spatial reach (for example, use of local services, neighborhood visits). Crucially, only activities with middle to high spatial reach and low intensity of use (for example, living, working, or recreating in low densities) are best served by the car system. This is because in these cases only the speed and the flexibility of the car cannot be matched by the alternatives.

The diagram in figure 2 can be usefully employed to characterize existing urban systems. Los Angeles, for instance, is a city where most activity and mobility patterns fall into the `car environment' type; Hong Kong can be best characterized as a `transit environment'; and many European historic city centers still function as `walking and cycling environments'. The diagram can, however, also be used in a more normative way, and this is the central thesis of this paper: it is a combination of environments exploiting the specificities of each that allows the highest accessibility with the lowest dependence on the car, or `urban development without more mobility by car'. In other words, where transport modes other than the car are or can be a competitive way of linking spatially disjointed activities, transport, land use, and other policy measures should enhance rather than frustrate this possibility.

The essential elements of the ensuing multimodal urban ^ regional morphology are illustrated in figure 3, where a schematic transport infrastructure network determines the Urban reach high intensity of use

Regional reach, high intensity of use

Regional reach, lower intensity of use (car)

Local reach (walk, cycle)

Urban transit (mean distance 3 km) Regional transit (mean distance 30 km) Interregional transit (mean distance 300 km)

Interregional reach, high intensity of use

Origins (homes)

Destinations (workplaces, other facilities)

Highway

Figure 3. Principles of multimodal urban ^ regional development: morphological scheme.

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location of activities according to their spatial reach and intensity of use, following the criteria identified in figure 2. Activities with high spatial reach and high intensity of use are around transit nodes; activities with low spatial reach are in walking and cycling environments; and only activities with middle to high spatial reach and low intensity of use are dependent on the use of the car. In practice, either the spatial pattern of activities or the pattern of the transport infrastructure could be the starting point of development.

In the following sections we discuss developments in the Amsterdam urban region in the Netherlands in order to underpin empirically the strategy being suggested here.

In section 4 we introduce the region and its historical and current transport and landuse patterns. In section 5 we show some evidence of `urban development without more mobility by car' at the level of the whole urban region. In section 6 we extend the analysis to local components of the region following the environment types identified in figures 2 and 3.

4 Transport and land-use patterns in the Amsterdam urban region The Amsterdam urban region is an intriguing example of a development pattern which, in many ways, recalls the ideal typical model illustrated in figures 2 and 3.

Its structure is partly planned and has partly emerged out of historic patterns and market trends. Behind the instantaneous picture there is, of course, a continuous transformation process marked by all sorts of contradictions and discussions. Our objective in this paper is, however, not so much to explain how all this came about (although this is a very relevant point and intriguing story), nor to take a stand on current dilemmas (for this, see le Clercq and Bertolini, 2003), but rather to explore whether such an urban ^ regional development pattern can be an effective one.

The network that can be detected in figure 4 is built upon the historic pattern of the city of Amsterdam and other cities around it, such as Haarlem, Zaanstad, and Hilversum. These smaller cities have become specialized centers in the region: for example, Haarlem is a tourist center, but also accommodates the headquarters of a major international publisher and other publishing-related activities; Zaanstad originally hosted a number of food-processing industries and is still the location of the international headquarters of Ahold (the retailer); Hilversum was one of the first residential suburbs of Amsterdam (together with the Haarlem area), and today boasts an impressive concentration of broadcasting organizations, etc. Planned, more recent, centers outside Amsterdam include new towns such as Hoofddorp near Schiphol airport and, most importantly, Almere which is located on land that was reclaimed as recently as the 1960s. With a population of around 150 000, Almere is the fastest expanding city in the Netherlands and is working strongly on its as yet relatively weak employment base by trying to attract advanced industries in the multimedia, leisure, and information and telecommunication sectors.

At the level of this evolving urban regional network, the central transport planning challenges of the last hundred years have been to develop adequate heavy rail linkages between secondary centers and the `mother' city of Amsterdam and, later, to connect the region into the national motorway grid. Today, with increasing specialization and the expansion of activities in the intermediate zones, the challenge is rather the development of a regional transit system and the introduction of hierarchies in the motorway system which will allow for the fact that different cities, towns, and major exurban activity concentrations function as complementary centers in a more horizontal fashion.

As far as the structure of the core city of Amsterdam is concerned, a crucial turn has been the development since the mid 1970s, of the motorway ring A10 and new railway links to the west (via Schiphol airport) and the east (via Almere). This has been

Urban development without more mobility by car?

0 Built-up areas Airport Seaport

5

581

10 km

Railway Motorway Railway station

Figure 4. The Amsterdam region, with main infrastructure and (sub)centers.

accompanied by the concentration of large offices and urban facilities alongside the newly constructed tangential infrastructure, particularly to the south of the core city (in locations such as Zuid and Bijlmer, also known as the `Zuidas', or `South Axis'). Current trends in the spatial distribution of activities in the city are a vivid example of how the growing differentiation in accessibility resulting from the evolution of the transport infrastructure has become an essential factor in shaping the transformation of the form and the use of the urban space. Intriguingly, many of the ideal typical combinations identified in section 3 of this paper are matched by these developments, and similar trends can be observed in smaller cities in the region.

As well as the historic city center (around Central Station, or CS in figure 4), which still enjoys the best accessibility by transit, several nodes have emerged which typically combine excellent accessibility both by public and by private transport. The most important of these new nodes is the international airport of Schiphol, which provides a unique combination of intercontinental air links and direct connection to the regional and national motorway and railway networks. The airport area has become the focus of a rich and diverse concentration of activities (including office, conference, hotel, retail, and logistics). Office rents there are the highest in the country and the employment baseรถat around 50 000รถis comparable with that in the historic city center.

Other older and newer nodes are also increasingly the focus of specific concentrations.

Large-scale office complexes, and financial and business services in particular, have been clustering around the railway stations of Sloterdijk (for example, Teleport), Lelylaan (World Fashion Centre), Amstel (Philips, Worldcom), Zuid (World Trade Center, the ABN ^ AMRO and ING banks). The area between Bijlmer station and the A2 motorway appears to be a preferred location for combined warehouse and office complexes,

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including an extremely dynamic information and communication technology (ICT) sector (with, among others, the European headquarters of Cisco). In these locations firms enjoy, as well as the availability of space, excellent access both to the regional labor market and to metropolitan facilities including the airport. Urban centers elsewhere in the region, such the previously mentioned Almere or Zaanstad, are also experiencing growth as business locations, particularly as far as back offices are concerned. Many specialized small-scale professional services have, on the other hand, remained faithful to the walking and cycling environment of the historic city center, which is also proving an ideal breeding ground for up and coming Internet and multimedia businesses.

A similar differentiation may be also observed in the distribution of urban facilities; most noticeably: new hospitals along the A10 motorway ring; the RAI congress and exhibition center, the Insurance Exchange, the District Tribunal and the Free University around Zuid station; and a giant retail and leisure complex at Bijlmer station. At the same time, more finely grained shopping, entertainment, and cultural activities have continued to thrive in the old city. Reinforcing this trend, after an unfortunate attempt at downtown-style office development between the 1980s and 1990s, a number of large cultural facilities have recently been or will shortly be opened along the southern IJ-river banks, east and west of Central Station.

In addition, and although the dynamism is somewhat more limited, residential choices (at least, of those who can choose!) also appear to be increasingly influenced by the differences between, in addition to other factors, more and less accessible, more and less intensely used, urban areas. For instance, the walking and cycling environments of the historic `canal belt' of Amsterdam and the car environments of the green suburbs of `t Gooi around Hilversum or Bloemendaal around Haarlem are both highly desired residential environments, albeit desired by different populations. Furthermore, there are signs of an emerging demand for high-quality apartments in the direct surroundings of the main multimodal nodes.

5 Mobility trends at the urban ^ regional level The process of specialization (which is partly market driven, partly planned) of the urban ^ regional space described above is currently being translated in a more deliberate strategy aimed at the development of a regional metropolis of complementary, connected, locations. Transport infrastructure is seen as a main tool in the structuring of this envisaged `network city'. The way in which this strategy is taking shape and the obstacles, particularly institutional, which are still in the way would be worth a paper in themselves. However, and as already stated, our central object in this paper is, rather, connecting this empirical evidence to the general argument on sustainability and accessibility. Is there any evidence of `urban development without more mobility by car' in the Amsterdam urban region? In order to answer this question we turn now to an analysis of the mobility patterns that have characterized the recent evolution of the region. In section 6 we break down the analysis to the level of the environment types identified in figures 2 and 3.

The diagrams in figures 5 and 6 illustrate how, in the Amsterdam region, growth in population and jobs has been matched by a stable modal split, where transit and the bicycle (walking is not included in these statistics) hold a significant, and even increasing share. In particular, figure 5 shows how the growth rate of car trips has been lower than both the growth rate of the population and the growth rate of jobs. Transit use is growing the fastest, as this, rather than car use, appears to cater for the increase in the scale of operation (from local to regional) of the urban system. This can be seen as an indication of the potential for the development of transit environments, and of the

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Growth

120

100

1990

1995

2000 Car trips

Population

Jobs

Transit trips

Bicycle trips

Figure 5. Amsterdam region: trends in the growth of population, jobs, and trips by mode between 1991 and 1998 (1991 ย 100; walking not included) (source: Dienst Infrastructuur, Verkeer en Vervoer, 2000).

100

Split (%)

80 60

23

23

23

25

54

52

40 20 0 1990

1995 Car

Public transport

2000 Bicycle

Figure 6. Amsterdam region: modal split trends between 1991 and 1998 (walking not included) (source: Dienst Infrastructuur, Verkeer en Vervoer, 2000).

realization of such potential. The growing scale of operation of the system may also partly explain the relative stagnation of bicycle use in the region.

All in all, the pattern in the Amsterdam region seems to suggest that the realization of the specific potential of all sorts of mobility environmentsรถcar, transit, and walking and cycling environmentsรถis a workable strategy which combines both accessibility (indirectly documented by the continuing growth in population and jobs) and sustainability (the relatively high share of environmentally friendly modes). As the qualitative description of trends in the spatial distribution of activities suggests, there appears in Amsterdam to be a high degree of (potential) complementarity between the different mobility environments. In the next section we explore this claim in some detail.

6 Mobility trends at the local level 6.1 Introduction

Analyses of activity and mobility patterns that match the environments identified in sections 3 and 4 of this paper are not standard, as infrastructure networks and their areas of influence, rather than administrative units, should be the leading criteria for the collection and analysis of data. However, there are some recent studies that do approximate this and provide useful insights in the emergence and evolution of mobility environments in the Amsterdam urban region. Three such studies are discussed in this section. The first is an analysis at the level of the whole Randstad, the highly urbanized

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area in the west of the Netherlands of which the Amsterdam urban region is a major component. The second set of data is focused on trends in different parts of Amsterdam.

The third study is focused on a particularly interesting section of the urban region and the city as typified in figure 4: the development corridor connecting some of the major, most dynamic, subcenters ömost notably including the Zuidas (South Axis).

6.2 Emerging modal specialization in the Randstad

Table 1 documents transport-mode trends, between 1986/87 and 1997 for a range of spatial relationships in the Randstad. For this purpose the Randstad has been divided into three area types: large cities, their agglomerations, and the rest (see figure 7). In the Amsterdam urban region, the large-city area type corresponds with the municipal Table 1. Randstad, modal split of all trips (other than walking) (source: Goudappel Coffeng, 1999b).

Type of relationshipa within lg lg ± owa lg ± lg lg ± ota lg ± r within a a±r within r Total

As % of all trips

Modal split 1986/87 (%)

1986/87

1997

car

36.7 6.5 2.2 1.3 8.8 12.7 3.8 27.9

33.3 6.8 2.9 1.8 9.1 12.8 4.6 28.6

49.2 0.5 66.1 4.7 67.3 26.6 81.2 10.8 71.2 9.1 52.9 0.1 80.1 3.0 54.4 0.4

100.0

100.0

56.2

train btm

2.3

b

Modal split 1997 (%) train btmb bicycle

bicycle

car

14.5 13.8 4.6 2.2 10.1 2.6 4.4 1.7

35.8 15.4 1.6 5.8 9.6 44.1 12.6 43.5

42.6 0.6 66.6 5.1 56.0 38.9 74.8 18.2 71.3 11.7 51.2 0.2 80.5 3.5 55.0 0.6

8.2

33.4

54.2

a

3.4

11.9 12.1 3.6 3.1 8.7 1.9 3.3 0.9

44.9 16.2 1.6 3.9 8.3 46.7 12.6 43.6

6.4

36.0

lgÐlarge city; aÐagglomeration; owaÐown agglomeration; otaÐother agglomeration; rÐrest of Randstad. b btmÐbus, tram, metro.

Large cities

Large-city agglomerations

Other

Figure 7. Randstad area types (source: Goudappel Coffeng, 1999b).

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territories of Amsterdam and Haarlem (roughly corresponding to the built-up areas in figure 4); neighboring municipalities constitute the agglomeration. Similar criteria have been adopted for other parts of the Randstad.

The data in table 1 reveal a marked modal specialization of relationship types. For instance, car and bicycle dominate mobility `within' all area types. The train has a significantly above-average share of large city ^ large city relationships and in large city ^ other agglomerations relationships. In all other long-distance relationships the car is virtually hegemonic. Especially intriguing in the context of this paper is that in most cases this specialization of mobility environmentsöand with it, arguably, their complementarityöhas been growing. Within agglomerations, the rest of the Randstad, and above all within large cities, the bicycle is increasing its share not only at the expense of public transport but also of the car, signaling the further consolidation of a walking and cycling environment there. Also, several car environments seem to be strengthening their profile, albeit less spectacularly, as trends in relationships with and within the rest of the Randstad testify. Third, trends in large city ^ large city, and large city ^ other agglomerations trips document the emergence of transit environments. The aggregate result of this increasing specialization is comparable with that for the Amsterdam urban region as shown in section 5: a stable, and relatively sustainable, modal split in the face of a growth in total mobility. As far as the future is concerned, possibly the most important question is whether public transport will be able to cater for the growth in the spatial scale of relationships, indirectly documented by the decreasing share of `within' trips. An alternative, or rather complementary, challenge is that of exploring the scope for containment of the growth of the average distance traveled, namely, by providing more spatial opportunities within a given area (through densification and diversification of land uses).

6.3 Modal trends within Amsterdam

Table 2 breaks down the trends discussed in section 6.2 at the Amsterdam municipality level. For this purpose, the city has been divided in three area types: the historic inner city, the prewar city, and the postwar city (see figure 8, over). Here too a growing modal specialization can be detected. In the historic inner city and in the prewar cityöor the city within the ring roadöthe bicycle has been reinforcing and gaining, respectively, a dominant position in total trips at the expense both of public transport and of the car. In the postwar cityöor the city outside of the ring roadöthe car has been strengthening its dominance, mainly at the expense of the bicycle. The cumulative modal trend at the scale of the municipality is that of a growing share of the bicycle in the total amount of trips, and a decline in the shares both of the car and of public transport, in the face of a 6% growth in households and a 4% growth in jobs between 1990 and 1997 within the municipality boundaries. This can be seen as a stable, and relatively sustainable, modal split. However, average travel distances, in particular and not surprisingly those by all forms of motorized transport, have been increasing Table 2. Modal split in the Amsterdam municipality, excluding walking (source: Dienst Infrastructuur, Verkeer en Vervoer, 1999a).

Mode

Public transport Bicycle Car

Historic inner city

Prewar city

Postwar city

Amsterdam

1980

1997

1980

1997

1980

1997

1980

1990

1997

25

21

27

24

25

25

28

26

25

42 33

53 27

32 40

40 36

28 47

22 53

30 42

32 42

35 40

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Historic inner city

Prewar city

Postwar city

0 Built-up areas Airport Seaport

5

10 km

Railway Motorway Railway station

Figure 8. Amsterdam area types (source: adapted from Dienst Infrastructuur, Verkeer en Vervoer, 1999a).

in the same period, resulting in a 31% growth of the per capita distance traveled by car between 1990 and 1997 (all data from Dienst Infrastructuur, Verkeer en Vervoer, 1999b).

This takes us back to the policy challenges identified in the preceding section: the need to significantly increase the share of public transport in the longer trips, or to limit the growth of average distances through land-use measures (or a combination of the two).

As far as the limitation of growth of average distances is concerned, modal trends in the prewar city are particularly interesting. Here, much infill development has taken place in the period under scrutiny. There is currently a shift of focus of this urban renewal effort (densification, diversification) to the postwar neighborhoods which could increase the scope for cycling and walking there as well. As far as the first challenge is concernedรถthe potential role of public transportรถthe analysis of modal choice before and after opening of the Ring Line metro in the next section also provides some interesting clues.

6.4 Mobility trends before and after opening of the Ring Line metro

Table 3 documents trends in the modal split of people working within the direct area of influence of the Ring Line metro (see figure 9), before and after its opening in 1997. This Table 3. Modal choice (excluding walking) of people working in the area of influence of the Ring Line metro, before and after its opening (source: Dienst Infrastructuur, Verkeer en Vervoer, 2001).

Type of trip

Home to work Business

Before opening of the Ring Line (%)

After opening of the Ring Line (%)

car

public transport

bicycle

car

public transport

bicycle

47 62

43 25

10 13

40 53

51 36

9 11

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0 Built-up areas Airport Seaport

Railway Metro Motorway

2.5

5 km

Railway station Area of influence

Figure 9. Area of influence of the Ring Line metro (source: adapted from Dienst Infrastructuur, Verkeer en Vervoer, 2001).

metro line is particularly important as it runs within a significant part of Amsterdam's most important growth corridor, connecting many of the nodes described in section 4 and including the Zuidas, or South AxisรถAmsterdam's most important office development location around Zuid station. The opening of the Ring Line has made this stretch of the growth corridor multimodal by all means: exceptionally accessible by car, national and regional train, and high-quality local public transport. This is not yet true of other parts of the corridor, most notably towards Schiphol, where a metro line is under discussion but not yet built.

The data in table 3 show two interesting things in the context of this paper. The first is that even in a relatively peripheral, highly dynamic, development area the modal split can be relatively sustainableรถif public transport provision is adequate. The second is that introduction of the Ring Line metro, or full realization of the multimodality of the corridor, has further increased this sustainability. These results appear even more important when put in the context of the spatial dynamics in the area of influence of the Ring Line metro. It is precisely in this part of the urban region where most growth of employment is expected in the future: an estimated 39.4% increase in jobs between 1996 and 2010, as opposed to a 1.8% increase in the area within the motorway ring, and a 31.8% increase in the rest of the agglomeration (Dienst Infrastructuur, Verkeer en Vervoer, 1999b). Interestingly, much of the expected employment growth in the rest of the agglomeration is concentrated in the airport area, stressing the importance of extending the metro system, and thus the multimodal corridor, in that direction.

7 Conclusions In the first part of this paper, a transport and land-use strategy linking the improvement of sustainability and of accessibility was sketched. In the second part, the

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example of the Amsterdam urban region was used to show that this is a workable strategy. A detailed discussion of the role of specific policy measures, as opposed to autonomous developments, in this evolution, although important, falls outside the scope of this paper (for this, see le Clercq and Bertolini, 2003). However, figure 1 can be usefully referred to in order to mention some of the main policy elements that have contributed to the trends described above. At the level of cycling and walking environments, an essential measure has been the widespread development of dedicated, most notably bicycle, infrastructure on the transport side, matched on the land-use side by the renewal of historic neighborhoods and the development of new mixed-use neighborhoods. As far as transit environments are concerned, substantial investment in upgrading and expanding train (for example, the new tangential links) and metro infrastructure (particularly the Ring Line) are important transport-policy elements.

Their impact has been positively reinforced by a land-use policy seeking the concentration of large-scale offices and regional facilities around public transportation nodes.

In addition, the most significant policy dealing with car environments has been the regulation of parking allowance, which has proved an invaluable tool in managing the accessibility of locations, most notably within the municipality of Amsterdam.

With the help of figure 1, some of the upcoming challenges can be identified. At the level of `without travel' mobility environmentsรถhardly addressed by policy up to nowรถit could prove important to broaden the possibilities for teleworking and other teleactivities by providing larger housing and perhaps also adjoining working space and/or allowing for more flexible use. Increasingly, most businesses start in the home but are soon constrained by space limitations. Investment in walking and cycling infrastructure is still needed, but the continued success of walking and cycling environments also depends on the extent to which new and existing residential areas are able to develop a critical mass of destinations (such as workplaces and facilities) within short distances. As already mentioned, an essential condition for the support of transit environments is that of the development of a comprehensive regional transit network or, more precisely, making the current fragments function in a more integrated fashion.

The success of transit environments will, however, largely depend on land-use trends and policies. The concentration around multimodal nodes of large-scale offices and regional facilities remains crucial in this respect. Some of the major upcoming challenges concern car environments, where accessibility management of the sort implemented through parking regulations in the core city needs to be gradually extended to the whole region and connected to measures to manage capacity on the motorway network, including downgrading and upgrading of sections of the systems, road pricing, and possibly a few new strategic links. Perhaps the main problem here is that of the poor political acceptability of many such measures.

In more general terms, and perhaps most importantly, the fine-tuning of the demand for and the supply of accessibility should become a more explicit goal of transport and land-use planning than now is the case. If this does not happen, upcoming challenges risk going unnoticed, and the positive results of past years may be put at risk. In cities around the world the question of how to allow for a sustainable and yet accessible urban system is a major issue. The specific answers to this question need, of course, to be found in each local context. Other cities may be already more successful than Amsterdam in this. However, in this paper we hope to have made at least two things clear. The first is that there is much to be gained by striving for synergy rather than competition in the contribution of different transport modes, including nonmotorized ones, to enhancing accessibility. The second is that a condition essential to the achievement of such synergy is the fine-tuning of the supply of mobility, as provided by the transport system, and the demand for mobility, as originated by

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different land-use patterns. The approach presented in this paper may offer a useful way to conceptualize this task as well as offering potential solutions.

Acknowledgements. We gratefully acknowledge the Ministry of Economic Affairs of the Netherlands for financing through the Netherlands Agency for Energy and the Environment (NOVEM) this research project. NOVEM has also provided useful feedback.

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